On the evening of 4th May 1844, the screw-propelled steamship ‘Severn’ cast off from the riverside wharf headed for Bristol. The tide was running strongly up the river, but the captain was confident his high-pressure steam engine and Archimedes screw (an early version of the modern propeller) would carry him safely against the stream.
Unfortunately the captain did not think to check his equipment in advance. As the ship swung out into the river, the crew found that the propeller had become jammed by a length of chain. The tide swept the ‘Severn’ against the bridge, smashing holes in the hull and eventually sinking her. No lives were lost, but the ship, which was only a few weeks old, was a write off.